The Effects of Myopia on Optic Disc Morphology and Retinal Vascular Geometry: A Study of Anisometropic Eyes

Purpose: The purpose of this study was to investigate the effect of myopia on the optic disc morphology and retinal vascular geometry in anisometropic eyes. Methods: This self-controlled study included 49 subjects with bilateral myopic anisometropia ≥2.0 diopters (D). Computer-assisted programs were used to measure optic disc morphology (disc diameter, cup‑to‑disc ratio, and ovality index) and retinal vascular geometry (central retinal vascular caliber, fractal dimension [FD], tortuosity, and branching parameters). Paired-samples t-tests assessed interocular parameter differences; independent-samples t-tests compared these interocular differences between anisometropia subgroups (<4 D vs. ≥4 D). Scatter plots and linear regression were used to analyze the correlation between interocular parameter differences and anisometropia severity. Results: More myopic eyes showed significantly smaller optic disc horizontal diameters (P < 0.001), lower cup-to-disc ratio (P = 0.004), and greater ovality index (P < 0.001), as well as reduced arteriolar FD (P = 0.038) and venular FD (P = 0.023). The interocular differences in arteriolar FD (P < 0.001), angular asymmetry (P = 0.031), asymmetry ratio (P = 0.023), and junctional exponent deviation (JED) (P = 0.011) differed significantly between the two anisometropia subgroups. Increasing anisometropia was associated with greater interocular differences in arteriolar FD (P = 0.005) and venular FD (P = 0.005), and with a more negative interocular difference in arteriolar JED (P = 0.028). Conclusions: In myopic anisometropia, the more myopic eye has smaller and more tilted optic discs and a lower FD; interocular differences in FD and JED correlate with anisometropia degree. Translational Relevance: These findings enhance understanding of optic disc and retinal vascular changes in the myopic fundus.